The present invention relates to a cooler for cooling particulate material which has been subjected to heat treatment in an industrial kiln, such as a rotary kiln for manufacturing cement clinker, which cooler comprises an inlet, an outlet, end walls, side walls, a bottom and a ceiling, at least one stationary supporting surface for receiving and supporting the material to be cooled, means for injecting cooling gas into the material, as well as a reciprocating scraper system which comprises a number of rows of scraper elements which extend transversely across the direction of movement of the material, said elements being moved back and forth in the direction of movement of the material in order to convey the material forward over the supporting surface.
In EP 0718578 a cooler of the aforementioned kind is described. In this known cooler, the scraper elements are made up of cross bars with a triangular cross-sectional profile, with the bars being mutually connected via chains and being moved back and forth on the supporting surface by means of chain wheels fitted at the ends of the supporting surface. This known cooler has several drawbacks. Because of the high temperatures which occur in the cooler, and particularly at the inlet end of the cooler, as well as the substantial forces which are required to convey the material through the cooler, the chains must be designed with relatively large dimensions. As a result, the chains will form so-called shadow areas of equivalent size, i.e. areas in which the chains obstruct the upward-flowing cooling gas so that the overlying material is not cooled as intended. Also, the cross bars in the known cooler are not firmly fixed to restrain them from moving, neither perpendicularly to the material's direction of movement nor in terms of rotation about their own longitudinal axis. In cases where a larger body of material is to be conveyed through the cooler, one or several cross bars may therefore be forced vertically upwards, and may come to ride on the body. This will reduce the conveyance of material through the cooler. In cases where a cross bar is lifted at one side only, the cross bar will also be able to move towards one side of the cooler, thereby giving rise to operational disorders. Rotation of one or several of the cross bars may have an adverse effect on the efficiency of conveyance. Furthermore, the known cooler is vulnerable to operational disorders, for example in event of rupture of a single chain link, given the necessity to shut down the cooler in order to undertake the necessary repair work. A further disadvantage of the known cooler is that the driving system in the form of the chains consists of wear parts which must be replaced at regular intervals.